If you care about a diverse newsroom, I think you should care about the concept of unpaid internships.
Are you certain of what you are suggesting?
Blacks and hispanics (assuming that is the diversity you are focused on) represent a far smaller percentage of college graduates than their percentage of the overall population (if I care about diversity, I should care about that too, FWIW). Which is the main point I'd make. You are simplifying a societal inequity that has deep roots.
Within that subset, though, in recent years at least, among graduating college seniors, those minority groups have represented a larger percentage of college internships than their actual numbers. The reason has been that a lot of industries and companies have been putting a focus on diversity . Maybe it's different in newsrooms, I don't know. But are you assuming something or are you telling me something that you know?
What you are getting at has much deeper roots than people deciding to do an unpaid internship, which aren't a "concept," as you put it, but a reality. You can't just mandate that people get paid something (regardless of their value), nor can you create money where it doesn't exist, and expect that it won't have unintended consequences. Most newsrooms are struggling places. Mandating that you pay unproductive workers isn't going to magically create diversity. Financial reality still exists.
The lack of a diversity in a lot of industries goes way beyond what you are suggesting. Unpaid internships largely didn't exist until the 1970s, when there was a huge rise in the number of college graduates. As the Federal government got more involved in trying to socially engineer society in the decades afterward, offering subsidized loans (that have now created a student debt crisis -- this is what happens when you try to socially engineer equality; there are often serious pecuniary effects that create bigger problems down the line), they effectively turned a college degree into what a high school degree had been (in practical terms, at least). At the same time, the job market got tougher as the U.S. started to slide (largely for similar reasons), and internships took on more and more importance to introduce raw college graduates with few skills into an increasingly tougher job market.
It's simply supply and demand. When you and your increasingly worthless college degree makes you look like a dime a dozen, and the demand for what you can offer is shrinking, an unpaid internship takes on even more importance in trying to separate yourself from the pack.
Does that create or perpetuate racial disparities? Undoubtedly. A big part of career is simply "who you know" and the person who did a summer internship has a leg up that the person who needed to work a fast food job. To the extent that shuts out racial minorities, it sucks (just as it sucks for MOST non-minorities). But hidden in what you posted (even though you didn't say it) is a suggestion of doing more of the same things that created and exacerbated that problem over the last several decades. When you start subsidizing things, taking away the ability to freely barter (which is all an internship is), trying to regulate behavior, etc., it's a formula for serious unitended and unanticipated consequences.
Even with that, though, because of people's social awareness (which has been people behaving on their own, attitudes changing organically), in recent years the reality has been that minorities who do end up a college path (again, a small percentage relative to their percentage of the total population. ... if you exclude Asians, at least), are not being shut out of internships. They are even slightly overrepresented now, relative to their numbers, BECAUSE people are focused on diversity. Is that not the case in newsrooms, and if so, is it because of your implication that financial hardship stands in their way more than it does for non-minorities?